1 //===-- StripDeadPrototypes.cpp - Remove unused function declarations ----===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass loops over all of the functions in the input module, looking for
11 // dead declarations and removes them. Dead declarations are declarations of
12 // functions for which no implementation is available (i.e., declarations for
13 // unused library functions).
14 //
15 //===----------------------------------------------------------------------===//
16
17 #define DEBUG_TYPE "strip-dead-prototypes"
18 #include "llvm/Transforms/IPO.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/Pass.h"
22 using namespace llvm;
23
24 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
25
26 namespace {
27
28 /// @brief Pass to remove unused function declarations.
29 class StripDeadPrototypesPass : public ModulePass {
30 public:
31 static char ID; // Pass identification, replacement for typeid
StripDeadPrototypesPass()32 StripDeadPrototypesPass() : ModulePass(ID) {
33 initializeStripDeadPrototypesPassPass(*PassRegistry::getPassRegistry());
34 }
35 virtual bool runOnModule(Module &M);
36 };
37
38 } // end anonymous namespace
39
40 char StripDeadPrototypesPass::ID = 0;
41 INITIALIZE_PASS(StripDeadPrototypesPass, "strip-dead-prototypes",
42 "Strip Unused Function Prototypes", false, false)
43
runOnModule(Module & M)44 bool StripDeadPrototypesPass::runOnModule(Module &M) {
45 bool MadeChange = false;
46
47 // Erase dead function prototypes.
48 for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
49 Function *F = I++;
50 // Function must be a prototype and unused.
51 if (F->isDeclaration() && F->use_empty()) {
52 F->eraseFromParent();
53 ++NumDeadPrototypes;
54 MadeChange = true;
55 }
56 }
57
58 // Erase dead global var prototypes.
59 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
60 I != E; ) {
61 GlobalVariable *GV = I++;
62 // Global must be a prototype and unused.
63 if (GV->isDeclaration() && GV->use_empty())
64 GV->eraseFromParent();
65 }
66
67 // Return an indication of whether we changed anything or not.
68 return MadeChange;
69 }
70
createStripDeadPrototypesPass()71 ModulePass *llvm::createStripDeadPrototypesPass() {
72 return new StripDeadPrototypesPass();
73 }
74